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Session 10 - Studies of Black Holes.
Display session, Monday, June 09
South Main Hall,
Advanced instruments for imaging in high energy X-ray astronomy may use the coded mask technique or focusing optics. In either case position-sensitive detectors are required with spatial resolution in the range of \sim 100 microns to 1 mm, depending on the angular resolution and focal length or mask-to- detector separation. The room temperature semiconductor, Cadmium-Zinc-Telluride (CZT), is a very attractive detector material for these applications. It can be used from <5 keV to >500 keV, provides superior energy resolution to NaI, and may be fabricated with simple ohmic contacts with sizes done to <100 microns, which can provide very fine spatial resolution. Pixel response may be obtained with true pixel contacts on one detector face or orthogonal crossed-strip contacts on opposite faces. The later scheme requires less electronics and is under development at UCSD and WU for applications in both focusing and coded mask systems. Detectors have been studied with tunable monochromatic X-ray beams and mapped with finely collimated 30 micron beams using a computer- controlled robotic measuring system. In particular, a 375 micron pitch crossed-strip detector has been studied in detail. These results show crossed-strip readout has good spatial and spectral capabilities. However, irregularities in charge collection through the detectors appears to limit the practical spatial resolution that may be achieved. Models of charge collection in the detectors have been developed and compared with laboratory tests. Results are presented on the detectors' spatial and spectral properties.
